This invention relates to a terminal block for use in wiring an immersion heater assembly and is more particularly concerned with improvements in an electrically insulating terminal block for supporting electrical heating elements and providing for simplified three phase wiring of the heating elements in a first face of the block or single phase wiring thereof in an opposite face.
Electric rod-type heating elements are commonly used in a variety of appliances, such as dishwashers, water heaters and stoves, to heat water or other fluid to a desired temperature. These heating elements generally consist of a resistance wire surrounded by a concentric sleeve of heat conductive and electrically insulating material, such as magnesium oxide, and an outer electrically and heat conductive metal sheath. Usually such heating elements are of a curved or U-shape such that leads of the heating element are relatively adjacent to facilitate electrical connection thereto. To this end, a terminal block is often provided for electrical connection of the leads of the heating elements and for additionally supporting the heating elements. The terminal block also provides a liquid-tight seal between the heating elements and the appliance.
Replacement of some of the heating elements or the terminal block may be necessary due to mechanical or electrical failures or because of other conditions, such as the accumulation of encrusting deposits upon the heating elements which reduce the heating efficiency thereof. In replacing some of the heater elements or the terminal block, it may not be known in advance whether the heating elements are wired to accommodate a single phase power source or a three phase power source. The serviceman must therefore be equipped to make appropriate electrical connections for either type of power source. It is generally easier and less expensive to appropriately wire the heating elements than it is to change to a different phase power source.
Terminal blocks for supporting immersion type electrical heater assemblies have been developed heretofore for use in the field where it may be desirable to connect the heating elements in parallel for a single phase load, as by forming electrical connections between leads of the heating elements with straps or jumpers. Alternatively, it may be desirable to connect the heating elements in a delta configuration, with a different arrangement of the straps between heating element leads, for a three-phase load. Many prior art terminal blocks require attention during the installation procedure to provide adequate electrical clearances or spacing between the lead connection straps or jumpers, or employ insulating washers and fishpaper which necessitates the use of additional materials and increases the time required to mount and install the heating elements. Many of the prior art terminal blocks also present all six leads from the heating elements for either single phase or three phase wiring on a single surface or face of the terminal block. This further complicates the wiring procedures and increases the likelihood that at least some of the heating elements will be miswired. For instance, if one of the heating elements has both leads electrically connected, the heating element is thereby shorted such that no electrical power is applied thereto and, accordingly, the heating element will not provide any heat. Miswiring of the heating elements may not be noticed until the appliance is reassembled and tested thereby resulting in a considerable loss of labor in correcting the wiring. If adequate testing or inspection is not performed, any miswiring may go unnoticed which can, depending upon the application, result in substandard performance of the appliance.